Thermodynamics of a laptop computer

By Stephen Bucaro That desk in front of you and everything else around you is made up of atoms.

Thermodynamics of a laptop computer

Ruler scale is in millimeters. Typically, a vacuum pump is used to remove the air from the empty heat pipe. The heat pipe is partially filled with a working fluid and then sealed. The working fluid mass is chosen so that the Thermodynamics of a laptop computer pipe contains both vapor and liquid over the operating temperature range.

Below the operating temperature, the liquid is too cold and cannot vaporize into a gas. Above the operating temperature, all the liquid has turned to gas, and the environmental temperature is too high for any of the gas to condense.

Whether too high or too low, thermal conduction is still possible through the walls of the heat pipe, but at a greatly reduced rate of thermal transfer. For the heat pipe to transfer heat, it must contain saturated liquid and its vapor gas phase.

The saturated liquid vaporizes and travels to the condenser, where it is cooled and turned back to a saturated liquid. In a standard heat pipe, the condensed liquid is returned to the evaporator using a wick structure exerting a capillary action on the liquid phase of the working fluid.

Wick structures used in heat pipes include sintered metal powderscreen, and grooved wicks, which have a series of grooves parallel to the pipe axis. When the condenser is located above the evaporator in a gravitational field, gravity can return the liquid. In this case, the heat pipe is a thermosiphon.

Finally, rotating heat pipes use centrifugal forces to return liquid from the condenser to the evaporator. Heat pipes contain no mechanical moving parts and typically require no maintenance, though non-condensable gases that diffuse through the pipe's walls, resulting from breakdown of the working fluid or as impurities extant in the material, may eventually reduce the pipe's effectiveness at transferring heat.

The advantage of heat pipes over many other heat-dissipation mechanisms is their great efficiency in transferring heat.

A pipe one inch in diameter and two feet long can transfer 3. Heat pipes are designed for very long term operation with no maintenance, so the heat pipe wall and wick must be compatible with the working fluid. For example, water in an aluminum envelope will develop large amounts of non-condensable gas over a few hours or days, preventing normal operation of the heat pipe.

In a heat pipe life test, heat pipes are operated for long periods of time, and monitored for problems such as non-condensable gas generation, material transport, and corrosion. This is by far the most common type of heat pipe. Aluminum envelope with ammonia working fluid for Spacecraft Thermal Control.

Superalloy envelope with alkali metal cesium, potassium, sodium working fluid for high temperature heat pipes, most commonly used for calibrating primary temperature measurement devices.

There are two main applications for vapor chambers. First, they are used when high powers and heat fluxes are applied to a relatively small evaporator. After the vapor condenses on the condenser surfaces, capillary forces in the wick return the condensate to the evaporator.

Note that most vapor chambers are insensitive to gravity, and will still operate when inverted, with the evaporator above the condenser. In this application, the vapor chamber acts as a heat flux transformer, cooling a high heat flux from an electronic chip or laser diode, and transforming it to a lower heat flux that can be removed by natural or forced convection.

It is possible to produce flat heat pipes as thin as 1. In these heat pipes, the temperature drops linearly as the power or condenser temperature is reduced.

For some applications, such as satellite or research balloon thermal control, the electronics will be overcooled at low powers, or at the low sink temperatures. Variable Conductance Heat Pipes VCHPs are used to passively maintain the temperature of the electronics being cooled as power and sink conditions change.

A reservoir, and 2. When the heat pipe is not operating, the NCG and working fluid vapor are mixed throughout the heat pipe vapor space. Most of the NCG is located in the reservoir, while the remainder blocks a portion of the heat pipe condenser. The VCHP works by varying the active length of the condenser.

When the power or heat sink temperature is increased, the heat pipe vapor temperature and pressure increase.

Thermodynamics of a laptop computer

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By Stephen Bucaro. That desk in front of you and everything else around you is made up of atoms. An atom consists of electrons orbiting around a barnweddingvt.com  · Thermodynamics is a prerequisite for many follow-on courses, like heat transfer, internal combustion engines, propulsion, and gas dynamics, to name a few.

-What will this class prepare me for in the real world? Let's take a desktop computer or a laptop computer.

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Thermodynamics of a laptop computer

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